[S]alvatore said:
^^^yes but they don't take body composition into account. Would it be perfectly normal/healthy if 100lbs out of that 160 was fat?
Ok you also have to take common sense into account too

. If you're all fat and within the normal indices, that is a different story. Having a lot of fat is not healthy no matter what height/weight you are.
Me for example, I have very little body fat. I am not going to brag and say I'm all cut, because I am not. However, I am the type that can work out for only a little while and I will develop definition really quickly because I am mostly lean muscle and not fat. To some people I seem a bit too light for my weight....but that is only because I do not carry much fat. That is just how my body works and how nature made me.
Consider the lion and the cheetah. The cheetah has an average weight of about 130 lbs and is about 1.5 m long on average. The lion has an average weight of 390 lbs and is about 2.5 m long on average. The lion is 3 times the weight but not even twice the length. They were just built differently. Nature intended it that way.
Should the cheetah gain 100 lbs just to be on par with the lion's weight? Does that make any sense? There are advantages and disadvantages of being heavy vs light. The cheetah takes advantage of its relatively light weight to outrun bigger enemies and prey. The lion relies on its strength to maintain its terrirtory against small enemies.
The point is, lions and cheetahs don't try to fight nature. Neither should you. If you are in a perfectly healthy condition, don't gain or lose weight just because it is something to do or because someone tells you to. Work on your inner core and you will see much greater rewards than gaining a few pounds.